Configuration method and system

ABSTRACT

The present invention relates to a configuration method and system for providing a configuration parameter, such as a server, gateway or proxy server address(es), to a terminal device. A trigger control information defining trigger events and/or conditions is loaded to the terminal device ( 11, 21 ) and a discovery procedure for obtaining the configuration parameter(s) is initiated when at least one of the trigger events and/or conditions is detected. Thereby, a user-friendly automatic configuration of services or server addresses can be provided to a moving mobile terminal.

FIELD OF THE INVENTION

The present invention relates to a method and system for providing aconfiguration parameter such as an address of a data source, e.g. aserver, a gateway or a proxy server, to a terminal device.

BACKGROUND OF THE INVENTION

Discovery procedures are required to discover addresses or otherconfiguration parameters of data sources or servers for providingservices to a terminal device or client. According to the Dynamic HostConfiguration Protocol (DHCP), as specified in the Internet EngineeringTask Force Request For Comments (IETF RFC) 2608, a dynamic allocation ofnetwork addresses is defined, where temporary or permanent network (IP)addresses are allocated to hosts. The basic mechanism for the dynamicallocation of network addresses is simple. A client requests the use ofan address for some period of time. The allocation mechanism guaranteesnot to reallocate that address within the requested time and attempts toreturn the same network address each time the client requests anaddress. To achieve this, the client broadcasts a DHCP discover messagewhich is passed on to DHCP servers not on the same physical subnet. Eachserver may then respond with a DHCP offer message that includes anavailable network address and/or other configuration parameters. Theclient receives one or more DHCP offer messages from one or more serversand may choose one server from which to request configurationparameters, based on the configuration parameters offered in thereceived DHCP offer messages. Then, the client broadcasts a DHCP requestmessage including the server identifier to indicate which server it hasselected, such that those servers not selected by the DHCP requestmessage may use the message as a notification that the client hasdeclined that servers offer. The server selected in the DHCP requestmessage commits the binding for the client to persistent storage andresponse with a DHCP acknowledge message containing the configurationparameters for the requesting client.

According to the Domain Name Server (DNS) protocol specification asdefined e.g. in the IETF RFC 1035, domain names are used as arguments toa local agent, called a resolver, which retrieves information associatedwith the domain name. Thus, a user might ask for the host address ormail information associated with a particular domain name. To enable theuser to request a particular type of information, an appropriate querytype is passed to the resolver with the domain name. The resolver isresponsible for hiding the distribution of data among name servers fromthe user. The resolver starts with knowledge of at least one nameserver. When the resolver processes a user query it asks a known nameserver for the information. In return, the resolver either receives thedesired information or a referral to another name server. Using thesereferrals, resolvers learn the identities and contents of other nameservers. Resolvers are responsible for dealing with the distribution ofthe domain space and dealing with the effects of name server failure byconsulting redundant data bases in other servers.

Previously, the internet server systems and thus also theirconfiguration parameters (e.g. addresses) have been quite stable andthey have been configured manually based on user specific settings tothe terminal. However, in the case of wireless Internet, for exampleWLANs (Wireless Local Area Networks), the configuration using DHCP andDNS protocols does not take into consideration wide area cellular typerapid mobility. In particular, a mobile station or mobile terminal maysend a DHCP query in order to find an IP address of a P-CSCF (Proxy CallState Control Function) or some other service lookup server. The DHCPserver in the network answers with a P-CSCF address. Then, the mobileterminal contacts the P-CSCF in order to get a list of availablemultimedia services. The P-CSCF can take into account the type ofnetwork to which it is contacted, so that not all of the servicesdesigned for the PS (Packet-Switched) domain may technically be possiblein the CS (Circuit-Switched) domain for example because of the lowcapacity of the CS network. The P-CSCF answers with a list of serviceswhich are now available to the user.

In mobile Internet, the dynamic configuration of the configurationparameters (e.g. server addresses) should be adapted to the movements ofthe mobile terminal. Solutions for such a dynamic service configurationare provided by the Service Location Protocol (SLP) specified in theITEF RFC 2608, which provides a scalable framework for discovery andselection of network services. A user agent which is a process workingon the users behalf to establish contact with some service by retrievingservice information from service agents or directory agents performsdiscovery by issuing service request messages. Furthermore, a ServiceDiscovery Protocol (SDP) is specified in the Bluetooth SpecificationVersion 1.0 B issued on 29. November 1999 by the Bluetooth Forum, wherea service discovery mechanism is provided as a means for clientapplications to discover the existence of services provided by serverapplications as well as the attributes of those services. The attributesor configuration parameters of a service include the type or class ofservice offered and the mechanism or protocol information needed toutilize the service. A set of SDP server available to an SDP client canchange dynamically based on the RF (Radio Frequency) proximity of theservers to the client. When a server becomes available, a potentialclient must be notified that the client can use SDP to query the serverabout its services. Similarly, when a server leaves proximity or becomesunavailable for any reason, the client may use SDP to poll the serverand may infer that the server is not available if it no longer responseto requests.

However, these known dynamic service configuration procedures do notprovide an automatic server address configuration or reconfigurationprocedure and a service configuration customization mechanism.

When a mobile terminal moves across the radio, network and service areacoverage, it is a problem for the user to manually configure server orproxy server addresses. In practice, it is almost impossible toconfigure the addresses manually, because the user cannot be aware ofthe current service configuration of the operator. This is especiallytrue when localized area specific servers of a visited operator areconsidered. For example, a user is abroad and wants to find out specialoffers of local restaurants and the like. Thus, an automatic andoperator specific service configuration is highly desirable.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand system for providing a configuration parameter to a terminal device,by means of which an automatic and operator specific serviceconfiguration can be achieved.

This object is achieved by a method for providing a configurationparameter of a data source to a terminal device, said method comprisingthe steps of:

-   loading a trigger control information into the terminal device, the    trigger control information defining trigger events and/or    conditions; and-   initiating a discovery procedure for obtaining the configuration    parameter when at least one of the trigger events and/or conditions    is detected.

Furthermore, the above object is achieved by a system for providing aconfiguration parameter of a data source to a terminal device, wherein anetwork to which the terminal device is connected is arranged to load atrigger control information defining trigger events and/or conditionsinto the terminal device, and wherein the terminal device is arranged toinitiate a discovery procedure for obtaining the configuration parameterwhen at least one of the trigger event and/or conditions is detected.

Additionally, the above object is achieved by a terminal device for acellular network, comprising storing means for storing a trigger controlinformation defining trigger events and/or conditions; and

-   trigger means for initiating a discovery procedure for obtaining a    configuration parameter when at least one of the trigger events    and/or conditions is detected.

Accordingly, a new configuration or reconfiguration mechanism andprocedure for server address discovery is provided, where the triggercontrol information defines event and/or conditions which shall triggerthe discovery procedure of configuration parameters, such as serveraddresses, to be executed. When a triggering event or condition comestrue, the procedure is started to get new configuration parameters ofservers or proxy servers and their services from the network to be usedby the terminal device. Thereby, a user-friendly automatic configurationof server or proxy server addresses or other service configurationparameters can be provided to the user terminal.

The terminal device may be a mobile terminal and the data source may beany server or proxy server for providing a service to the mobileterminal.

The configuration parameter may be an address of a WWW proxy, a WAPgateway, a WAP push server, a proxy VoIP and Multimedia CSCF server, alocalized service area specific server or a defined geographical areaspecific server.

Preferably, the trigger control information may be stored in a SIM(Subscriber Identity Module) or USIM (UMTS SIM) card or a volatilememory of the terminal device. Thereby, an initial operator specificconfiguration can be provided when the SIM or USIM card is inserted intothe terminal device.

The network may be arranged to load the trigger control information intothe terminal device by an updating procedure using a SIM application.Thus, the initial trigger control information can be updated based on achange in the network environment due to a movement of the terminaldevice.

Furthermore, the trigger control information may be broadcast by thenetwork in a system information message.

Additionally, the network may be arranged to deliver the trigger controlinformation to the terminal device in a dedicated manner when theterminal device registers to the network. In this case, the triggercontrol information may be delivered together with server addresses,according to the related user profile or as a part of it, using anysignalling protocol, such as DHCP, SM, SLP or SIP (Session InitiationProtocol) for example.

The trigger control information may be interpreted by the terminaldevice, and the defined service configuration triggers may be stored inthe cellular terminal device.

The discovery procedure may comprise a request for new server addressesfrom the network, and the new server addresses may be delivered to theterminal device by a service configuration response message.

The trigger events and/or conditions may comprise at least one of a cellupdate, a routing area update, a location area update, a change in theIP network point of attachment, a localized service area change, adefined geographical area change, a location of all mobiles ingeographical area change, a roaming, and a movement outside a predefinedgeographical area.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be described in greaterdetail on the basis of a preferred embodiment with reference to theaccompanying drawings, in which

FIG. 1 shows a schematic diagram indicating initialization, storing andchanging of a trigger control information in a terminal device inaccording to the preferred embodiment,

FIG. 2 shows a signaling diagram indicating a service configurationprocedure according to the preferred embodiment,

FIG. 3 shows a schematic block diagram of a terminal device according tothe preferred embodiment, and

FIG. 4 shows an example of a route of a mobile terminal and associatedtrigger events.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment will now be described on the basis of a mobileterminal connected to a cellular network such as a 3rd generation mobilecommunication network comprising a circuit-switched core network and apacket-switched core network.

In the context of the present invention, a service is understood to beany entity that can provide information, perform an action, or control aresource on behalf of another entity. A service may be implemented assoftware, hardware, or a combination of hardware and software.Furthermore, the term proxy is used to indicate any mechanism wherebyone system “fronts for” another system in responding to protocolrequests. Proxy systems or servers are used in network management toavoid having to implement full protocol stacks in simple devices, suchas modems.

FIG. 1 shows a schematic diagram of an initialization, storing andchanging procedure of a trigger control information. The operator of anetwork 30 may define available or used service configuration triggersand may provide them as a trigger control information to a firstterminal equipment or mobile terminal 11 and a second terminal equipmentor mobile terminal 21. These mobile terminals 11, 21 comprise a USIM(Universal Mobile Telecommunications System Subscriber Identity Module)or non-volatile memory 12, 22, e.g. an BEPROM (Electrically ErasableProgrammable Read-Only-Memory), in which the trigger control informationcan be stored. The trigger control information defines events and/orconditions, which shall trigger a server address discovery procedure orany other procedure for obtaining configuration parameters of servers orother data sources, to be executed. The server addresses can beaddresses of a WWW (World Wide Web) proxy, a WAP (Wireless ApplicationProtocol) gateway, a WAP push server, a proxy VoIP (Voice over IP) andMultimedia CSCF server, a localized service area specific server, adefined geographical area specific server etc.

When a triggering event or condition comes true, e.g. is detected by thefirst mobile terminal 11 and/or the second mobile terminal 21, aconfiguration or reconfiguration procedure is started to get new serveraddresses or other configuration parameters from the network 30 to beused by the terminal. A control information can be initialized, changedand stored in the following ways, depending on the operator and userneeds and an agreement between them:

In step 1, the operator of the network 30 can initialize the triggercontrol information and store it in the USIMs 12, 22 of the first andsecond mobile terminals 11, 21 when the USIM card is sold to thecustomer. Then, it can be updated later e.g. by using a SIM applicationtool kit or other similar solutions. As an alternative, the triggercontrol information can be stored in the non-volatile memory (e.g.EEPROM) of the first and second terminals 11, 21. In any case, theoperator can allow a user to change the trigger control informationand/or the operator can also change it using the mechanisms described instep 3 and/or step 4.

In step 2, the changed trigger control information is then stored in theUSIMs or BEPROM 12, 22 of the first and second mobile terminals 11, 21.

As indicated by step 3, the operator may broadcast changes in thetrigger control information as a part of a system information message.This is a particularly applicable when the trigger control informationof a plurality of mobile terminals registered to the network 30 is to becontrolled.

As an alternative or in addition thereto, step 4 indicates a provisionof the trigger control information to a second mobile terminal 21 in adedicated manner, when the second mobile terminal 21 registers to thenetwork 30. This may be achieved e.g. during the delivery of serveraddresses to the second mobile terminal 21 according to a user profileor as a part of it using any signalling protocol, such as DHCP, SM(session/service management), SLP or SIP for example.

Thus, the first and second mobile terminals 11, 21 are continuouslyprovided with an updated trigger control information adapted to theircurrent location. The address or other configuration parameter discoveryprocedure may be performed as follows. When the mobile terminal detectsor determines a trigger event or trigger condition as defined by thestored trigger control information, it may send a SLP query in order toobtain an IP address of a WWW proxy or some other required proxy server.Also DHCP query may be triggered in order to obtain an IP address of arespective CSCF or some other service lookup server. For example, when aPS mobile terminal enters a (new) CS network, the queried DHCP serveranswers with a P-CSCF address. The mobile terminal may then contact theP-CSCF in order to get a list of available multimedia services. TheP-CSCF can take into account the type of network where it is connected,so that not all, of the services designated for the PS domain maytechnically be possible in the CS domain, e.g. due to the low capacityof the CS network. The P-CSCF answers with a corresponding list ofservices, such that the user of the mobile terminal is now provided witha list of services available in the network.

It is noted that the any of the initially described discoveryprocedures, e.g. according to the DHCP or DNS protocol or SLP protocol,or other discovery protocols may be used for obtaining the requiredaddress or other configuration parameters.

FIG. 2 shows a signaling diagram of a service configuration procedurebetween the first mobile terminal 11 and the network 30. In step 1, thetrigger control information is provided for the mobile terminal 11 bythe network. This control information is then interpreted in step 2 bythe mobile terminal 11, and the defined service configuration triggersare then stored in the volatile memory and/or the USIM 21 of the mobileterminal 11. In step 3, a triggering event happens or locationconditions come true, as defined by the trigger control information, anda service configuration or reconfiguration procedure is started by themobile terminal 11. Thus, the mobile terminal 11 issues a serviceconfiguration request in step 4 so as to ask for new server addresses orother configuration parameters from the network 30. In step 5, the newserver addresses or other configuration parameters are delivered to themobile terminal 11 by a service configuration response message.

The operator of the network 30 may select the most suitable triggers forservice configuration or reconfiguration based on his own needs, i.e.service configuration customization, and may define them in the referredtrigger control information. As an example, the following events orconditions can be defined as triggers:

-   1. a cell update where a new cell is entered,-   2. a routing area update where a new routing area of a PS domain is    entered,-   3. a location area update where a new location area of a CS domain    is entered,-   4. a change in the IP network point of attachment, e.g. change of    GGSN (Gateway General Packet Radio Services Support node) or HA    (Home Agent),-   5. a change of a Localized Service Area (LSA), which is an    operator-defined area, for which specific access conditions apply    and which may correspond to an area in which the core network offers    specific services,-   6. a change of a Defined Geographical Area (DEGA),-   7. a change of the Location of All Mobiles in Geographical Area    (LAMGA),-   8. a roaming from a first PLMN to a second PLMN, by which also the    operator is changed, and-   9. a movement outside a predefined geographical area, which may    include position definition functions, e.g. Global Positioning    System (GPS) etc., in the mobile terminal 11 or the network 30.

Of course other suitable trigger events and/or conditions associatedwith a terminal movement or change of location can be defined.

FIG. 3 shows a schematic block diagram of the mobile terminal 11. It isnoted that only those functions relevant for the present invention areshown in FIG. 3. The mobile terminal 11 comprises a transceiver (TRX)113 for transmitting and receiving RF signals to/from the network 30.The TRX 113 is controlled by a signaling control unit 112 which isarranged to generate and interpret signaling messages transmitted to andreceived from the network 30, respectively. The signaling control unit112 is controlled by a trigger unit 111 based on the trigger controlinformation received from the network 30. An initial configuration orsetting of the trigger events and/or conditions may be obtained when aSIM or USIM card 101 is inserted into a USIM or SIM unit 110. Thetrigger control information of the SIM/USIM card 101 may then beinterpreted in the USIM or SIM unit 110, and the corresponding triggerevents and/or conditions may be supplied to the trigger unit 111. Basedon a corresponding signaling of the signaling control unit 112, whichindicates the receipt or detection of messages or other events andconditions, e.g. the triggers indicated above, the trigger unit 111 maythen decide whether to initiate a discovery procedure for obtaining therequired configuration parameters, e.g. server addresses of a server orproxy server.

Furthermore, the signaling control unit is arranged to perform orinitiate an update procedure when the trigger control information isreceived from the network 30 together with a broadcast signaling messageor a response message to a network registration procedure.

It is to be noted that the units or blocks 110 to 112 may be implementedas concrete hardware circuits or as software routines of a correspondingcontrol processor arranged in the mobile terminal 11.

The network operator may also define multiple triggers to be used. Anexample of such a case is shown in FIG. 4. FIG. 4 shows a moving routeof a mobile terminal through a network configuration comprising a firstnetwork PLMN-A and a second network PLMN-B. Both networks compriselocation areas LA, routing areas RA and individual cells. Some of theindividual cells are combined to a localized service area SOLSA with aspecific LSA identity. Furthermore, a defined geographical area (DEGA)with a predetermined DEGA identity and a location of all mobiles ingeographical area (LAMGA) with a predetermined LAMGA identity areprovided. When the mobile terminal moves according to a route indicatedby the arrow in FIG. 4, service reconfiguration procedures may beactivated several times at predetermined locations indicated on thearrow.

At a first location P1, a location area update is signaled by thesignaling control unit 112. Then, at a location P2, a routing areaupdate is signaled. Moreover, at the location P3, a DEGA change issignaled, and at the location P4 an LSA change is signaled. When themobile terminal enters the second network PLMN-B, an operator change isdetected due to the roaming from the first network PLMN-A to the secondPLMN-B. This may include a deregistration from the operator of the firstnetwork PLMN-A and a registration to the operator of the second networkPLMN-B. This may be accompanied by an initial service configuration. Atthe location P6, a LAMGA change is detected, and a cell update issignaled at the location P7. Finally, an additional LSA change isdetected at the location P8.

Based on the trigger control information and the correspondingregistered trigger events and/or conditions, a service configuration orreconfiguration procedure may be activated at predetermined ones or eachof the above locations P1 to P8.

It is noted that some of the above changes, updates may also trigger achange in the service provider. This is the case, when the networkoperator has rent a service area from one company and the other servicearea from another company. Thus, the service configuration procedureaccording to the present invention also enables a user-friendlymanagement of services in future mobile Internet systems as specifiede.g. in the 3GPP (3rd Generation Partnership Project) standardspecifications.

It is noted that the present application is not restricted to the abovepreferred embodiment, but can be applied in any network architecture,where service configuration parameters have to be downloaded ortransmitted from the network to a terminal device. Furthermore, anydesired trigger event and/or condition can be used for activating thediscovery procedure. The preferred embodiment may thus vary within thescope of the attached claims.

1. A method, comprising: loading a trigger control information providedby a network into a terminal device connected to said network, saidtrigger control information defining trigger events or conditions;interpreting, by the terminal device, said trigger control informationto determine the trigger events or conditions defined by said triggercontrol information; storing the determined trigger events or conditionsdefined by the interpreted trigger control information in a memory ofthe terminal device; initiating a discovery procedure at said terminaldevice for obtaining a configuration parameter used to identify a sourceof available multimedia services when at least one of said storedtrigger events or conditions is detected, wherein said discoveryprocedure comprises causing a request for new server addresses from saidnetwork to be transmitted, and receiving a service configurationresponse message comprising said new server addresses; and receiving alist of available multimedia services based on the discovery procedure,and wherein said loading the trigger control information comprisesinitializing the trigger control information by loading trigger controlinformation stored on a subscriber identity module card or on auniversal mobile telecommunications system subscriber identity modulecard in response to insertion of the subscriber identity module card orthe universal mobile telecommunications system subscriber identitymodule card into said terminal device.
 2. A method according to claim 1,wherein said terminal device comprises a mobile terminal and said datasource comprises a server configured to provide a service to said mobileterminal.
 3. A method according to claim 2, wherein said configurationparameter comprises an address of a server, a gateway or a proxy server.4. A method according to claim 1, wherein said discovery procedurecomprises an address discovery procedure according to a dynamic hostconfiguration protocol, domain name server protocol or service locationprotocol or some other discovery protocol.
 5. A method according toclaim 1, wherein said loading the trigger control information comprisesan updating procedure using a subscriber identity module application forupdating said trigger control information.
 6. A method according toclaim 1, wherein said trigger control information is stored in anon-volatile memory of said terminal device.
 7. A method according toclaim 1, further comprising receiving at least a portion of said triggercontrol information in a system information message broadcast from anetwork of said data source to said terminal device.
 8. A methodaccording to claim 1, wherein at least a portion of said trigger controlinformation is delivered to said terminal device when said terminaldevice registers to said network.
 9. A method according to claim 8,wherein said at least a portion of said trigger control information isdelivered in a dedicated manner into said terminal device together withserver addresses according to a user profile or a part of said userprofile using a signalling protocol.
 10. A method according to claim 1,wherein the at least one of said trigger events or conditions compriseat least one of a cell update, a routing area update, a location areaupdate, a change in the IP network point of attachment, a localizedservice area change, a defined geographical area change, a location ofall mobiles in geographical area change, roaming, or a movement outsidea predefined geographical area.
 11. A system, comprising a network and aterminal device connected to the network, wherein: the network isconfigured to load a trigger control information defining at least oneof trigger events or conditions into said terminal device; and saidterminal device is configured to interpret said trigger controlinformation to determine the at least one of trigger events orconditions defined by said trigger control information, store thedetermined at least one of trigger events or conditions defined by theinterpreted trigger control information in a memory of the terminaldevice, initiate a discovery procedure to obtain a configurationparameter used to identify a source of available multimedia serviceswhen at least one of said trigger events or conditions is detected, andconfigured to receive a list of available multimedia services based onthe discovery procedure, wherein said discovery procedure comprisescausing a request for new server addresses from said network to betransmitted, and receiving a service configuration response messagecomprising said new server addresses, and wherein said trigger controlinformation is loaded from a subscriber identity module or universalmobile telecommunications system subscriber identity module card whichis stored in said terminal device.
 12. A system according to claim 11,wherein said terminal device comprises a mobile terminal and said datasource comprises a server configured to provide a service to said mobileterminal.
 13. A system according to claim 11, wherein said configurationparameter comprises an address of a server, a gateway or a proxy server.14. A system according to claim 11, wherein said trigger controlinformation is stored in a non-volatile memory of said terminal device.15. A system according to claim 11, wherein said network is configuredto load said trigger control information into said terminal device by anupdating procedure using a subscriber identity module application.
 16. Asystem according to claim 11, wherein said network is configured tobroadcast said trigger control information in a system informationmessage.
 17. A system according to claim 11, wherein said network isconfigured to deliver said trigger control information to said terminaldevice when said terminal device registers to said network.
 18. Anapparatus comprising a terminal device, the terminal device comprising:a memory configured to store a trigger control information definingtrigger events or conditions, wherein said trigger control informationis provided for said terminal device by a network to which the terminaldevice is connected; and a trigger configured to initiate a discoveryprocedure to obtain a configuration parameter used to identify a sourceof available multimedia services when at least one of said triggerevents or conditions is detected, wherein said discovery procedurecomprises causing a request for new server addresses from said networkto be transmitted and receiving a service configuration response messagecomprising said new server addresses, and wherein the memory is furtherconfigured to receive a list of available multimedia services based onthe discovery procedure, and wherein the memory configured to store saidtrigger control information comprises a subscriber identity module oruniversal mobile telecommunications system subscriber identity modulecard which is stored in said terminal device, and wherein said triggercontrol information is interpreted by the terminal device within thememory to determine the trigger events or conditions defined by saidtrigger control information, and wherein the memory is furtherconfigured to store the determined trigger events or conditions definedby the interpreted trigger control information.
 19. An apparatusaccording to claim 18, wherein said memory comprises one or more of auniversal mobile telecommunications system subscriber identity module orsubscriber identity module card or a non-volatile memory.
 20. Anapparatus according to claim 19, further comprising an updaterconfigured to update said stored trigger control information in responseto a new trigger control information received from said network in abroadcast system control information or together with server addressesin a network registration procedure.
 21. An apparatus, comprising:storing means for storing a trigger control information defining triggerevents or conditions, wherein said trigger control information isprovided for said terminal device by a network to which the terminaldevice is connected; and trigger means for initiating a discoveryprocedure for obtaining a configuration parameter used to identify asource of available multimedia services when at least one of saidtrigger events or conditions is detected, wherein a list of availablemultimedia services is received in the storing means based on thediscovery procedure, and wherein said discovery procedure comprisescausing a request for new server addresses from said network to betransmitted, and receiving a service configuration response messagecomprising said new server addresses, and wherein said storing meanscomprises a subscriber identity module or universal mobiletelecommunications system subscriber identity module card which isstored in said terminal device, and said trigger control information isinterpreted by the terminal device within the storing means to determinethe trigger events or conditions defined by said trigger controlinformation, and wherein the storing means is further configured tostore the determined trigger events or conditions defined by theinterpreted trigger control information.
 22. An apparatus comprising aterminal device, the terminal device comprising at least one processorand at least one memory storing computer program code, wherein the atleast one memory and stored computer program code are configured to,with the at least one processor, cause the apparatus to at least:provide for storage of a trigger control information defining triggerevents or conditions on a subscriber identity module or universal mobiletelecommunications system subscriber identity module card stored in saidterminal device, wherein said trigger control information is providedfor said terminal device by a network to which said terminal device isconnected; interpret said trigger control information to determine thetrigger events or conditions defined by said trigger controlinformation; store the determined trigger events or conditions definedby the interpreted trigger control information; and initiate a discoveryprocedure to obtain a configuration parameter used to identify a sourceof available multimedia services when at least one of said triggerevents or conditions is detected, wherein the at least one memory andstored computer program code are configured to, with the at least oneprocessor, further cause the apparatus to receive a list of availablemultimedia services based on the discovery procedure, and wherein saiddiscovery procedure comprises the at least one memory and storedcomputer program code are configured to, with the at least oneprocessor, causing the apparatus to: provide for transmission of arequest for new server addresses from said network; and receive aservice configuration response message comprising said new serveraddresses.
 23. A computer readable medium storing a computer program,said computer program configured to control a processor to perform:loading a trigger control information provided by a network into aterminal device connected to said network, said trigger controlinformation defining trigger events or conditions, wherein said triggercontrol information is provided for said terminal device by said networkto which said terminal device is connected, and wherein said loading thetrigger control information comprises initializing the trigger controlinformation by loading trigger control information stored on asubscriber identity module card or on a universal mobiletelecommunications system subscriber identity module card in response toinsertion of the subscriber identity module card or the universal mobiletelecommunications system subscriber identity module card into saidterminal device; interpreting said trigger control information at theterminal device to determine the trigger events or conditions defined bysaid trigger control information; provide for storage of the determinedtrigger events or conditions defined by the interpreted trigger controlinformation in the terminal device; initiating a discovery procedure atsaid terminal device for obtaining a configuration parameter used toidentify a source of available multimedia services when at least one ofsaid trigger events or conditions is detected, wherein said discoveryprocedure comprises: provide for transmission of a request for newserver addresses from said network; and receiving a serviceconfiguration response message comprising said new server addresses; andreceiving a list of available multimedia services based on the discoveryprocedure.
 24. A method according to claim 9, wherein said signalingprotocol comprises dynamic host configuration protocol, session/servicemanagement protocol, service location protocol, or session initiationprotocol.